How to use asynchronous tasks to implement background processing in PHP

In web development, some tasks take a long time to complete, such as data processing, file uploading, email sending, etc. If these operations are performed in the foreground, it will lead to poor user experience and even cause the page to become unresponsive for a long time. Therefore, using asynchronous tasks can put these tasks in the background, improve the concurrency capability of the system, and also make the user experience and foreground interaction smoother.

As a popular server-side scripting language, PHP also has good support for implementing asynchronous tasks. This article will introduce how to use asynchronous tasks to implement background processing in PHP.

Principle and Method

The implementation principle of asynchronous tasks is to process the tasks in the background so that the program can perform other tasks during this period. This feature can be realized through the following PHP extension modules:

1. pcntl: realize background tasks through the Fork process.
2. posix: used to handle process-related system calls, such as signals, locks, etc.
3. swoole: A high-performance asynchronous, parallel, and coroutine network communication engine based on epoll technology.

Among them, swoole is the latest and most recommended extension module, which supports the most features, is the fastest, and has the strongest functions.

Use pcntl to implement background tasks

pcntl is a PHP extension that provides a set of process control functions. Through the pcntl_fork() function, a child process can be created to handle background tasks. The specific implementation method is as follows:

// 创建子进程
$pid = pcntl_fork();

if ($pid === -1) {
    die('could not fork');
}
// 父进程
elseif ($pid) {
    // 执行父进程代码...
    pcntl_wait($status);
}
// 子进程
else {
  // 执行子进程代码...
  exit;
}

In the above code, the pcntl_fork() function returns an integer value. If the value is -1, it means that the creation of the child process failed; if the value is 0, it means that it is currently a child process; If the value is greater than 0, it means that the current process is the parent process.

At this time, the child process can perform background tasks, such as scheduled tasks, file processing, etc. It should be noted that using pcntl should be avoided in an online environment because pcntl only works with command line scripts.

Use posix to implement background tasks

For web servers like Apache and Nginx, you need to use posix extensions for process management. posix provides some process management-related functions, such as posix_kill(), posix_getpid(), etc. Among them, the posix_kill() function can send signals to the process to control its behavior.

The method of using posix to implement background tasks is as follows:

// 创建子进程
$pid = posix_getpid();
$child_pid = pcntl_fork();

if (0 === $child_pid) {
  // 子进程代码...
  sleep(10);
  posix_kill($pid, SIGUSR1); //给父进程发送SIGUSR1信号
  exit();
}

// 父进程等待信号
pcntl_signal(SIGUSR1, function ($sig) {
  //在这里执行异步任务
  echo "Received signal: {$sig}
";
  die();
});

In the child process, the sleep() function represents the execution time of the asynchronous task. When the asynchronous task is executed, use the posix_kill() function to send the SIGUSR1 signal to the parent process, indicating that the task is completed. In the parent process, the pcntl_signal() function is used to wait for the arrival of the signal, which represents the completion of the asynchronous task.

Use swoole to implement background tasks

Swoole is a high-performance, asynchronous PHP coroutine framework that implements an asynchronous programming model in an event-driven manner. swoole provides a swoole_process class for managing the creation, execution and exit of child processes. The specific implementation code is as follows:

$process = new swoole_process(function (swoole_process $worker) {
  // 子进程执行的代码
});

$pid = $process->start();
$swoole_event_add($process->pipe, function ($pipe) use ($process) {
  $recv = $process->read();
  echo "received data: ". $recv;
});

$process->write('hello'); // 向子进程中发送消息

In the above code, a subprocess is created using the swoole_process class, and the subprocess can be started through the start() method. When the program in the child process needs to send a message to the main process, use the write() method to write data to the pipe. Another process can read the data in the pipe by listening to pipe events. In this way, inter-process communication is achieved, thereby implementing asynchronous tasks.

Summary

Asynchronous tasks are widely used in web development. Asynchronous tasks can be implemented in PHP through pcntl, posix, and swoole extensions. Among them, swoole is the most comprehensive and recommended method. By understanding these methods, developers can choose the appropriate method to implement asynchronous tasks based on specific business needs. This will help improve the system's concurrency capabilities and user experience.

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